Release mechanism for a pack-off shoe



Sept. 9, 1958 Filed March 25, 1954 c. c. CHIVENS ETAL 2,851,107

RELEASE MECHANISM FOR A PACK-OFF SHOE 2 Sheets-Sheet 1 INVENTOR. CLYDE c. GHIVENS a ROGER Q. FIELDS BY WW ATTORNEY Sept. 9, 1958 c. c. CHIVENS RELEASE MECHANISM FOR A PACK-OFF SHOE 2 Sheets-Sheet 2 Filed March 25, 1954 FIG.

INVENTOR. CLYDE C. CHlVENS- BY 8: ROGER Q.F\ELDS FIG.4

ATTORNEY nnrnasn MECHANISM rota A PACK-OFF SHOE tfllyde C. flhivens, Pasadena, Calif., and Roger Q. Fields, Houston, Tex, assignors, by mesne assignments, to Schlurnherger Well urveying Corporation, Houston, Tern, a corporation of Texas Application March 25, 1954, Serial No. 418,644

6 Claims. (Cl. 166-400) This invention relates to a novel release mechanism for a pack-E shoe adapted to engage the sidewall of a borehole and, more particularly, pertains to such a mechanism ideally suited for association with formation-fluidsampling apparatus and arranged to facilitate the withdrawal of the pack-off shoe from the sidewall of the borehole.

in an effort to obtain samples of formation fluid, free from contamination by the drilling fluid usually contained by a borehole, a pack-off shoe has been proposed which forms an excellent fluid seal with the sidewall of the borehole. Although formation-fluid-sampling appa ratus provided with such a pack-off shoe operates satisfactorily in obtaining a fluid sample, the seal is so effective that it is frequently difficult to withdraw the shoe from the sidewall in opposition to the hydrostatic pressure exerted by the column of drilling fluid in the borehole. Hence, sampling operations may be undesirably delayed.

It is, therefore, an object of the present invention to provide a novel release mechanism for a pack-off shoe.

Another object of the present invention is to provide a novel release mechanism for facilitating the withdrawal of a pacl -off shoe adapted to engage and form a good fluid seal with the sidewall of a borehole.

A further object of the present invention is to provide a novel release mechanism for increasing the speed of operation of a pack-off shoe of formation-fluid-sampling apparatus.

A release mechanism according to the invention may be associated with a pack-off shoe including a sealing face having a front surface adapted to engage the sidewall of a borehole and having a rear surface. The mechanism comprises a portion of the sealing face provided with a normally-closed channel extending between the front and rear surfaces of the sealing face. In order to facilitate retraction of the sealing face from the sidewall of the borehole, the mechanism further includes means for selectively opening the channel.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a perspective view of a complete sidewall fluid sampler incorporating a pack-off shoe associated with a release mechanism embodying the present invention and illustrating one portion of an operating cycle for the entire apparatus;

Fig. 2 is a cross sectional view taken along line 2-2 of Fig. l and drawn to an enlarged scale;

Fig. 3 is a side view of a portion of the apparatus of Fig. l, drawn to the scale of Fig. 2, but illustrating another portion of an operating cycle, certain parts thereof being shown cut-away and in section to reveal various interior details;

2,851,107 Patented Sept. 9, 19 58 Fig. 4 is a cross sectional view taken along line 44 I of Fig. 3; and

Fig. 5 is a View similar to that represented in Fig. 3, however, it illustrates yet another portion of an operating cycle for the apparatus.

In Fig. 1 of the drawings, the fluid sampler incorporating a pack-off shoe associated with a release mechanism embodying the present invention is shown disposed in a borehole 1i traversing earth formations 11, 12 and 13, and containing a drilling fluid 14, such as a water base or oil base mud. It is assumed that formation 12 is the one of interest from which a fluid sample is to be obtained.

The fluid sampler comprises upper and lower pressureresistant housing sections 15 and 16 connected together in longitudinally spaced relation by a pair of side rails 17 and 18 which, as shown in Fig. 2, are transversely spaced from one another. The device 15, 16 is suspended in the borehole It? by a cable 19 which, in connection with a winch (not shown) located at the surface of the earth, is employed to lower and to raise the device in the borehole in a customary manner.

In the vicinity of side rails 17 and 18, there is disposed a normally-retracted pad or pack-off shoe 20 of the type disclosed in the .copending application of Harry B. Boller, filed March 25, 1954, bearing the Serial Number 418,650 and assigned to the same assignee as is the present application. Shoe 20 is of generally oval shape and comprises a sealing face 21 constructed of a sheet of flexible material such as rubber. It has a fore portion provided with a central insert 22 having upper and lower apertures 23 and 24, the functions of which will be described in detail hereinafter. Sealing face 21 is connected at a plurality of peripheral points to a generally oval-shaped, horizontally-curved support ring 25 defining a curved reference plane that is concave with respect to a longitudinal axis for device 15, 16. In the normally-retracted position of shoe 20, the central portion of face 21 containing insert 22 is spaced from this reference plane in a direction away from the longitudinal axis of the device. In other words, the distance along the surface of face 21 between any pair of opposite points on ring 25 is longer than the straight-line distance between such points. Support member 25 preferably is of channel-like cross section and receives the entire peripheral edge of face 21.

As best shown in Fig. 3, a horizontally-curved driving plate 26 is welded, or otherwise peripherally connected, to support ring 25. It is provided with a central opening 27 through which insert 22 may pass and is connected to upper and lower driving pistons 28 and 29. Each of the pistons 28 and 29 is associated with one of hydraulic cylinders 30 and 31 of upper and lower cylinder housings 32 and 33 which are positioned between and secured to side rails 17 and 18. The cylinders and pistons just described are oriented so as to impart transverse movement to driving plate 26 between a retracted and an operative position relative to the longitudinal axis of device 15, 16.

The housings 32 and 33 are further provided with hydraulic cylinders 34 and 35 which receive pistons 36 and 37 respectively. The latter pistons are connected to a horizontally-curved back-up pad or shoe 38 arranged for movement in a direction opposite to that of shoe 20.

Each of a pair of tension springs 39 and 40 is connected at its extremities to adjacent end portions of driving plate 26 and back-up shoe 38. They are arranged to bias the plate and the shoe toward 'One another and maintain them in normally-retracted positions shown in Figs. 1 and 2.

In order to permit the shoes 20 and 38 to attain relatively close, normally-retracted positions, driving plate 26 is provided with upper and lower openings 41 and 42 for receiving the rear portions of cylinders 34 and 35. Shoe 38 is similarly provided with openings 43 and 44 for receiving cylinders and 31.

The cylinders 30, 31, 34 and 35 are fluidly connected to a hydraulic actuator (not shown) which may be disposed in upper housing section 15. This actuator may, for example, be of the type described in the copending application of Lawrence C. Chambers, filed April 7, 1950, and assigned the Serial Number 154,468, now Patent No. 2,674,313 for utilizing the pressure of borehole fluid 14 to drive pistons 28, 29, 36 and 37 in opposition to the bias of springs 39 and 40. Of course, any

well-known system for imparting movement to plate 26 I and to shoe 38 may be employed, such as a motor-driven screw-type jack.

To penetrate a desired formation and thereby facilitate the flow of formation fluid, the device is provided with a sample gun supported within a channel 46 of a gun housing 47. Housing 47 is bolted or otherwise secured to insert 22 with a spacer 48 disposed therebetween. It is thus movable with the insert in a horizontal direction out of and into the space defined by side rails 17 and 18 and piston housings 32 and 33.

Gun 45 contains a bullet 49 and has a barrel 50 aligned with port 24 in insert 22. A frangible plug or seal 51 normally blocks fluid communication between channel 46 and openings 52 and 53 in members 47 and 48 which are aligned with port 24.

Gun barrel 50 is provided with a plurality of radial openings 54 so that, as shown in Fig. 4, the interior of the barrel is in fluid communication with a channel 55 connecting channel 46 with a downwardly bent tube 56. The end of tube 56 is received by a flexible tube 57 which extends along rail 17, but is free to move so as not to inhibit movement of gun housing 47. The latter tube is connected to a sample-receiving chamber (not shown) in lower housing section 16. This chamber may be of any well-known construction, or may be of the type described in the aforementioned Chambers application, for obtaining a uniform, representative sample of formation fluid.

Inasmuch as the seal provided by face 21 may be so effective that shoe 20 cannot be retracted after a fluid sample is obtained, there is provided a release mechanism embodying the present invention. In this connection, gun housing 47 includes a channel 58 that receives a get-away gun 59. The gun contains a bullet 60 and its barrel 61 is aligned with port 23 of insert 22, as Well as with openings 62 and 63 in members 47 and 48. A frangible plug 64 normally blocks fluid communication between openings 58 and 62 and another frangible plug 65 in port 23 normally blocks fluid communication between the outer and inner surfaces of face 21 which may occur via port 23 and a connecting, vertically-extending channel 66.

The various control circuits for the hydraulic actuator (not shown) of housing 15 and for the guns 45 and 59 are completed via insulated electrical conductors of cable 19. These circuits may be of any conventional arrangement or as arranged in the Chambers application.

In operation, housing 15, 16 is lowered in borehole 10 by means of cable 19 to a position wherein insert 22 is adjacent the formation to be tested; in this example, it is formation 12. Plugs 51 and 64 serve to prevent the entry of drilling fluid 14 into gun barrels 50 and 61 in this initial portion of an operating cycle.

Hydraulic fluid pressure is then applied to cylinders 30, 31, 34 and 35 so that pistons 28, 29, 36 and 37 are displaced to move driving plate 26 and back-up shoe 38 in opposition to the bias of springs 39 and 40 toward the sidewall of the borehole. As is evident from Fig. 2, the configuration of shoe 20 is such that the central, fore portion of sealing face 21 containing insert 22 is the first to engage the sidewall. Thereafter, drilling fluid is displaced from the space between the sidewall and the 4 sealing face as additional portions thereof move toward and engage the sidewall, while, at the same time, backup shoe 38 engages the opposite section of the sidewall.

Since the surface distance along sealing face 21 between any pair of opposite points on ring 25 is longer than the linear distance between such points, tangential forces are developed in the sealing face. That is, compressive or compactive lateral forces are developed in the sealing face which tend to reduce its surface area. Since the sealing face is made of rubber, forces transverse to the lateral forces are developed and the face material tends to become thicker. Consequently, the outer surface of the sealing face is forcibly urged against the sidewall of borehole 10.

By reason of this constructional and operational feature, when the sampler is in the portion of an operating cycle illustrated in Fig. 3, the sealing face 21 engages and conforms to a relatively large section of the sidewall. It thus provides a very effective fluid seal between the sidewall of the borehole 10 and drilling fluid 14.

Of course, movement of insert 22 is accompanied by displacement of gun housing 47 and after shoes 20 and 38 are firmly positioned, gun 45 is fired to discharge bullet 49. The bullet ruptures frangible plug 51, passes through openings 52, 53 and 24 and comes to rest at a position in formation 12 designated in dash outline 49. if the gas or oil contained in formation 12 is in producible form, it is under some pressure and may thus flow into the opening in the formation created by the bullet and into the sample-receiving chamber (not shown) of housing section 16 via a path including port 24, openings 53 and 52, gun barrel 50, radial openings 54, channels 46 and 55, and tubes 56 and 57. The fluid sample continues to flow into the sample chamber for an interval of time suflicient to permit entry of a desired quantity. Thereafter, the sample chamber is closed and the device is ready to be brought to the surface.

However, before housing 15, 16 may be raised, shoes 20 and 38 must be retracted. To this end, the hydraulic pressure on pistons 28, 29, 36 and 37 is reduced approximately to atmospheric pressure and the hydrostatic pressure of the mud 14 acting on the pistons via the shoes, together with the bias of springs 39 and 40, displaces the shoes toward one another.

Because of the close conformity of sealing face 21 and the sidewall of the borehole, the sealing face may act as a suction cup. That is, this conformity plus the pressure of drilling fluid 14 on the rear surface of face 21, normally higher than the pressure of fluids in formations 12 on its front surface, is such that the springs 39 and 40, although they retract driving plate 26 as shown in Fig. 5, are unable to draw the face from engagement with the sidewall. In this event, get-away gun 59 is fired. Its bullet 60 ruptures frangible plugs 64 and 65 and opens a fluid path between the front and rear surfaces of the sealing face 21 via port 23 and channel 66, as shown in Fig. 5. Since borehole fluid can now flow through channel 66 and port 23, the pressure differential between these surfaces is equalized and shoe 20 may be retracted.

Accordingly, with both shoes 20 and 38 retracted in the final phase of an operating cycle, the fluid sampler may be withdrawn from borehole 10. At the surface, the sample-receiving chamber (not shown) can he removed from housing section 16 and the sample therein analyzed.

From the foregoing description, it is evident that the release mechanism constructed in accordance with the present invention facilitates retraction of a pack-off shoe from the sidewall of a borehole. Accordingly, the reliability and speed of a sampling run in improved.

Although the release mechanism embodying the present invention has been illustrated in the environment of a pack-off shoe in a particular type of fluid sampler, obviously it may be used in any other application wherein a fluid seal or a close association between the shoe and the sidewall of the borehole must be interrupted.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

I. A release mechanism for a pack-off shoe for use in a borehole containing a fluid at a pressure higher than the fluid pressure in an adjacent earth formation and including a sealing member having a front surface adapted to engage the sidewall of the borehole and having a rear 7 surface adapted to be exposed to the fluid in the borehole, said mechanism comprising a portion of said sealing member having a normally-closed channel extending between said front and said rear surfaces of said sealing member and adapted, when opened, to provide communi cation between the borehole sidewall engaged by said front surface and the borehole fluid to which said rear surface is exposed, and means for opening said channel.

2. A release mechanism for a pack-off shoe for use in a borehole containing a fluid at a pressure higher than the fluid pressure in an adjacent earth formation and including a sealing member having a front surface adapted to engage the sidewall of the borehole and having a rear surface adapted to be exposed to the fluid in the borehole, said mechanism comprising a portion of said sealing member having a channel extending between said front and said rear surfaces of said sealing member and adapted, when opened, to provide communication between the borehole sidewall engaged by said front surface and the borehole fluid to which said rear surface is exposed, a frangible plug disposed in said channel for normally closing said channel to fluid flow, and means for rupturing said plug thereby to open said channel to fluid flow/ 3. A release mechanism for a pack-off shoe for use in a borehole containing a fluid at a pressure higher than the fluid pressure in an adjacent earth formation and including a flexible sealing member having a front surface adapted to engage the sidewall of the borehole, having a rear surface adapted to be exposed to the fluid in the borehole and provided with an essentially centrally located opening, said mechanism comprising a relatively rigid insert closing said opening of said sealing member, said insert having one surface effectively forming a continuation of said front surface over said opening and another surface behind the rear surface of said sealing member adapted to be exposed to the borehole fluid, means forming a first channel in said insert extending from said one surface essentially transversely relative thereto, means forming a second channel in said insert extending from said first channel to said another surface of said insert, said first and second channels being adapted to provide communication between the borehole sidewall adjacent said insert one surface and the borehole fluid to which said insert another surface is exposed, closure means for normally closing said first channel in a section thereof intermediate said front surface of said sealing member and said second channel, and means for opening said closure means to open a fluid path between said front and said rear surfaces of said sealing member.

4. A release mechanism for a pack-off shoe as defined in claim 3 in which the closure means comprises a frangible plug disposed in said first channel for normally closing said first channel in a section thereof intermediate said front surface of said sealing member and said second channel, and the means for opening said closure means comprises explosively-operable means aligned with said first channel for rupturing said frangible plug to open a fluid path between said front and said rear surfaces of said sealing member.

5. A release mechanism for a pack-off shoe as defined in claim' 3 in which the closure means comprises a frangible plug disposed in said first channel for normally closing said first channel in a section thereof intermediate said front surface of said sealing member and said second channel, and the means for opening said closure means comprises explosively-operable means mechanically connected to said insert for simultaneous movement therewith and aligned with said first channel for rupturing said frangible plug to open a fluid path between said front and said rear surfaces of said sealing member.

6. Apparatus for use in a borehole containing a fluid at a pressure higher than the fluid pressure of an adjacent earth formation comprising: a sealing member including a front surface adapted to engage the sidewall of the borehole and a rear surface adapted to be exposed to the fluid in the borehole such that the pressure gradient between the higher borehole pressure and the lower forma tion pressure will normally tend to hold the sealing member against the formation, a portion of said sealing member having a channel therethrough for establishing fluid communication between said front and said rear surfaces; means for normally closing said channel to fluid flow; and means operative on said last-mentioned means for opening said channel to fluid flow.

References Cited in the file of this patent UNITED STATES PATENTS 2,233,930 Witt Mar. 4, 1941 2,671,510 Slick et al Mar. 9, 1954 2,674,313 Chambers Apr. 6, 1954 

